Re: UBSAN: Undefined behaviour in drivers/scsi/aic7xxx/aic7xxx_core.c:2831:31

Ilia Mirkin
2016-05-12T21:56:08Z

On Thu, May 12, 2016 at 4:08 PM, James Bottomley
<jejb@linux.vnet.ibm.com> wrote:
> On Thu, 2016-05-12 at 19:02 +0300, Meelis Roos wrote:
>> This is from a dual-AthlonMP 32-bit x86 system with onboard Adaptec
>> SCSI
>> controller, once during bootup.
>>
>> [ 4.896307]
>> =====================================================================
>> ===========
>> [ 4.896471] UBSAN: Undefined behaviour in
>> drivers/scsi/aic7xxx/aic7xxx_core.c:2831:31
>> [ 4.896629] shift exponent -1 is negative
>
> Is this some sort of false positive? The shift in question is
>
> devinfo->target_mask = (0x01 << devinfo->target_offset);
>
> The code which calls this in ahc_linux_initialize_scsi_bus() looks to
> be looping from 0-16 (or variations). Since the value passed in is
> unsigned, it would have to be set to ~0, which doesn't seem possible.

It's getting called from ahc_reset_channel, which does:

ahc_compile_devinfo(&devinfo,
CAM_TARGET_WILDCARD,
CAM_TARGET_WILDCARD,
CAM_LUN_WILDCARD,
channel, ROLE_UNKNOWN);

drivers/scsi/aic7xxx/cam.h:#define CAM_TARGET_WILDCARD ((u_int)~0)

-ilia